Vulnerability of high latitude soil organic carbon in North America to disturbance

Transcription

1 Vulnerability of high latitude soil organic carbon in to disturbance Guido Grosse, U Alaska Fairbanks Jennifer Harden, USGS Merritt Turetsky, U Guelph A. David McGuire, USGS Philip Camill, Bowdoin College Charles Tarnocai, Agrifood Canada Steve Frolking, U New Hampshire Edward A.G. Schuur, U Florida Torre Jorgenson, Alaska Ecoscience Sergei Marchenko, U Alaska Fairbanks Vladimir Romanovsky, U Alaska Fairbanks Kimberly P. Wickland, USGS Nancy French, Michigan Tech Mark Waldrop, USGS Laura Bourgeau-Chavez, Michigan Tech Robert G. Striegl, USGS Support NASA Carbon Cycle Sciences, NASA Terrestrial Ecology, NASA Interdisciplinary Sciences, NSF ARC, USGS Global Change Programs, others 2011 AmeriFluxand 3rd NACP All-Investigators Meeting New Orleans, 31 Jan 4 Feb 2011

2 Motivation + Goals Core reference list for this presentation: Grosse et al. (in press, 2011): Vulnerability and feedbacks of permafrost to climate change. EOS Trans. AGU. Grosse et al. (in review, 2011): Vulnerability of high latitude soil carbon in to disturbance. JGR Biogeosciences. McGuire et al. (2009): Sensitivity of the carbon cycle in the Arctic to climate change. Ecological Monographs, 79(4), 2009, pp Tarnocaiet al.(2009): Soil organic carbon pools in the northern circumpolar permafrost region, Global Biogeochem. Cycles, 23, GB2023. Marchenko et al. (2011): Soil temperature response to 21st century global warming: the role of and some implications for peat carbon in thawing permafrost soils in. Earth Syst. Dynam. Discuss., 2, Other references cited: Romanovskyet al. (2007): Chapter 7: Frozen Ground, in Global Outlook for Ice and Snow, edited, pp , Earthprint, UNEP/GRID, Arendal, Norway. Tarnocaiet al. (2007a): Northern Circumpolar Soil Carbon Database, Digital Database, Research Branch, Agriculture and Agri-Food Canada, Ottawa, Canada. Tarnocai et al. (2007b): Carbon Cycles in the Permafrost Region of, in The First State of the Carbon Cycle Report (SOCCR): The n Carbon Budget and Implications for the Global Carbon Cycle. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research,pp , National Oceanic and Atmospheric Administration, Climate Program Office, Silver Spring, MD, USA. Walter et al. (2007): Methane bubbling from northern lakes: present and future contributions to the global methane budget, Phil. Trans. R. Soc. A, 365(1856), Lehner, B., and P. Döll(2004): Development and validation of a global database of lakes, reservoirs and wetlands, Journal of Hydrology, 296(1-4), Strieglet al. (2005): A decrease in discharge-normalized DOC export by the Yukon River during summer through autumn, Geophys. Res. Lett., 32, L21413, doi: /2005gl Brown et al. (1997): Circum-Arctic Map of Permafrost and Ground Ice Conditions, U.S. Geological Survey, Reston, VA. Grosse et al. (in review, 2011): Thermokarst lakes, drainage, and drained basins. ELSEVIER Treatise on Geomorphology. Grosse et al.: Disturbance of soil organic carbon in high latitudes

3 Motivation + Goals high latitudes - Tundra and boreal forest ecoregions(45-83 N, W) - Large portion (but not all) is characterized by permafrost, ranging from continuous extent in the north to isolated patches in the southern zones Grosse et al., in review (JGR) [based on Brown et al.1997 and The Nature Conservancy 2008] Grosse et al.: Disturbance of soil organic carbon in high latitudes

4 Goals Motivation + Goals (1) Review the current soil organic carbon (SOC) storage in northern high latitude soils of (2) Describe key ecosystem, climate, and soil processes that characterize SOC pools in this region (3) Discuss major press and pulse disturbances and their impacts on northern high latitude SOC (4) Evaluate model projections of disturbance impacts on northern high latitude SOC (5) Discuss research and that need to be addressed to better predict the near-future trajectory of SOC in the North America high latitude regions Grosse et al.: Disturbance of soil organic carbon in high latitudes

5 Motivation + Goals Disturbance and vulnerability of SOC Disturbances -Perturbation of a normal stateor regime -Events or processes that significantly redistribute Camong major reservoirs -Alter key ecosystem factors in ways that affect the dynamics of the northern high latitude SOC pool -Have always been a natural factor for northern soil C dynamics Vulnerability -SOC pools are vulnerable if disturbance can significantly alter the physical, chemical and/or biological properties of the soil -Biological origin as well as physical and chemical preservation of organic matter can affect its vulnerability to disturbance Grosse et al.: Disturbance of soil organic carbon in high latitudes

6 Soil organic carbon pools Motivation + Goals Northern high latitude SOC pool is a dynamic stock Affected by: - C inputs (organic litter quality and quantity) -C stabilization (permafrost aggradation; cryoturbation; peat accumulation; sedimentation) - C destabilization (microbial decomposition; combustion) -C exports (via dissolved and particulate organic matter; inorganic and organic state; gas fluxes) Northern high latitude soils are often defined by low inputs; However, strong stabilization, decreased destabilization, and low exports result in long-term soil C sinks Panarctic SOC pools are very large: Pg SOC (McGuire et al., 2009) ; 1672 Pg SOC (Tarnocai et al., 2009) 818 Pg in Cryosols from 0-3 m depth (permafrost-affected soils) 277 Pg in frozen and unfrozen peatlands0 m to full depth 88% of the C pool are in perennially frozen soils + deposits (permafrost) 12% are in seasonally frozen soils + deposits within the permafrost region Grosse et al.: Disturbance of soil organic carbon in high latitudes

7 Soil organic carbon pools Motivation + Goals Seward Peninsula, AK Prince Rupert area, BC Colville River, AK Photo: G. Grosse Near-surface soil organic carbon in Cryosols Near-surface and deep soil organic carbon in frozen and unfrozen peatlands Photo: D. Vitt Photo: G. Grosse Organic carbon in deep permafrost deposits Grosse et al., in review (JGR) Grosse et al.: Disturbance of soil organic carbon in high latitudes

8 High latitude SOC pools in Motivation + Goals Grosse et al., in review (JGR) [based on Tarnocaiet al.2005, 2007 and Roberts et al. 2006] Pg C Permafrost region: 5.17x10 6 km 2 mineral soils 1.04x10 6 km 2 organic soils % Grosse et al.: Disturbance of soil organic carbon in high latitudes % 22% 12% m depth Depth Soil carbon mass (Pg) in n permafrost region Mineral soils Organic soils (peatlands) All soils Perennially Unfrozen Total Perennially Unfrozen Total Total frozen frozen m m m [Tarnocai et al., 2007, 2009]

9 Motivation + Goals T long-term, slow T, W Warming / cooling of soils W, T Vegetation changes Press disturbances W T, W Top-down permafrost thawing / permafrost formation T, W Changes in soil microbial communities Hydrological changes Increase in pace of disturbance Increase in spatial scale of disturbance W Changes in pedological processes Coastal and fluvial erosion W W Floods Droughts Erosion, Burial W, T Pulse disturbances short term, rapid W, T Thermokarst Wildfires T Nearsurface SOC stocks Increasing poten ntial of disturbance impacting dee eper SOC stocks Deeper sedimentary SOC stocks C gain C loss Grosse et al., in review JGR Grosse et al.: Disturbance of soil organic carbon in high latitudes

10 Press disturbance: Top-down permafrost thawing Motivation + Goals Segregated ground ice Photo: G. Grosse Active Layer Permafrost Ice wedge ground ice Photo: B. Jones CO 2 /CH 4 CO 2 /CH 4 METABOLISM Soil DOM Active Layer Permafrost METABOLISM METABOLISM M Soil DOM Soil DOM Grosse et al.: Disturbance of soil organic carbon in high latitudes Photo: K. Wickland Hydrologic Transport to surface waters Figure adapted from Striegl et al., 2005, GRL

11 Press disturbance: Top-down permafrost thawing Motivation + Goals ca ca x 0.5 GIPL model by Romanovskyet al Zone of thawing permafrost is defined as reaching a seasonal thaw depth in excess of 2 m See also: Marchenko et al. (2011) Zone of thawing surface permafrost by 2050 Zone of thawing surface permafrost by 2100 Cryosolarea within zone of thawing surface permafrost* 385,000 km 2 1,132,000 km 2 SOC mass upper 1 m* 9.7 Pg C 28.6 Pg C Grosse et al., in review JGR * Based on Tarnocai et al., 2007 Grosse et al.: Disturbance of soil organic carbon in high latitudes

12 Motivation + Goals Pulse disturbance: Thermokarst lakes Walter et al., 2007 (Phil. Trans. Royal Soc. A) Global Grosse et al., in review (Elsevier Treatise on Geomorphology) (based on Lehner& Döll, 2004) Ground ice content* Medium High Area of Cryosols # 714,000 km 2 887,000 km 2 SOC mass upper 1 m # 21.4 Pg C 33.2 Pg C *Brown et al., 1997 # Tarnocai et al., 2007 Grosse et al.: Disturbance of soil organic carbon in high latitudes

13 Pulse disturbance: Fires Motivation + Goals - Combustion of soil organic matter - Fire severity, size, duration -Complex post-fire feedbacks: albedo, soil thermal regime, permafrost thaw, hydrology, vegetation succession Future trend: increased fire severity; extended fire season; accelerated fire repeat cycles; increased likelihood of tundra fires Photo: B. Jones Photo: S. Marchenko Grosse et al.: Disturbance of soil organic carbon in high latitudes

14 Motivation + Goals Post-disturbance fate of northern high latitude SOC Fate of SOC in a post-disturbance setting depends on 1) whether the SOC remains in unaffected layers or becomes exposed to disturbances (depth) 2) whether the SOC is perennially frozen or subject to freezethaw cycles (temperature) 3) whether the ice or water content is high or low (water content) 4) soil organic matter quality as determined by botanic origin and long-term decomposition trajectories (lability) Photo: M. Turetsky Photo: T. Jorgenson Photo: T. Jorgenson Grosse et al.: Disturbance of soil organic carbon in high latitudes

15 Motivation + Goals projecting SOC disturbances Much progress over the last decade in integrating soil freezethaw dynamics, hydrology, and biogeochemistry in large-scale ecosystem models that simulate northern high latitude SOC dynamics No models are yet able to fully consider how changes in hydrology and soil thermal dynamics associated with disturbance influence soil carbon dynamics at high latitudes Main obstacles are implementation of complex feedback dynamics and sub-grid factors and processes Example: Permafrost modeling can successful project top-down permafrost thawing; however, highly dynamic and local-scale feedbacks with ground ice distribution, hydrology, and vegetation succession are not sufficiently implemented to factor in thermokarst and -erosion Grosse et al.: Disturbance of soil organic carbon in high latitudes

16 Motivation + Goals Research and 1. Uncertainties in SOC spatial distribution, i.e. deep stocks 2. Uncertainties in distribution and physical properties (thermal state, ground ice content) of permafrost 3. Enhancement of process understanding: post-disturbance SOC dynamics; vegetation succession; cryoturbation; time scales; hydrology 4. Modeling of SOC disturbances, feedbacks, and subgridprocesses on various scales 5. Further development of remote sensing methods for quantifying disturbances 6. How will disturbance frequencies + intensities and successional trajectories change in the future? 7. Integration of disturbances in dynamic Earth system models Grosse et al. (in review, 2011): Vulnerability of high latitude soil carbon in North America to disturbance. JGR Biogeosciences. Grosse et al. (in press, 2011): Vulnerability and feedbacks of arctic permafrost to climate change. EOS Trans. AGU. Grosse et al.: Disturbance of soil organic carbon in high latitudes